The present invention relates to an electrically conductive lamellar carbon composition. More specifically, it relates to a composition of carbon of a graphite-like structure which has been intercalated with nitronium or nitrosyl salts.
It has long been known that the unique crystalline structure of carbon having a graphite-like form makes it anisotropic with respect to conducting electrons. Its structure basically comprises stacked planes of aromatically bound carbon atoms. Hence, above and below each of such planes are the .pi. bonded electrons. These electrons have been said to contribute to the anisotropic conductive behavior, the conductivity being in a direction parallel to the aromatic carbon planes. This conductivity is approximately 5% that of copper.
Several compounds which show an increase in conductivity over that of graphite and graphite-like forms of carbon have been described in the literature. Ubbeholde, for example, has found that the intercalated compound formed from graphite and nitric acid has a conductivity somewhat similar to that of copper (0.6.times.10.sup.6 ohms cm.sup.-1) when measured parallel to the aromatic planes (A. R. Ubbeholde, Proc. Roy. Soc., A304,25, 1968). Oltowski has similarly found that interaction of vermicular graphite with halogen compounds and compression to a high density structure produces a moderately conductive material [U.S. Pat. No. 3,409,563]. Further intercalation compounds include La Lancette's preparation of graphite intercalated with antimony pentafluoride [U.S. Pat. No. 3,950,262]; Cohen's Lewis acid-fluorine intercalation compounds of graphite [U.S. Pat. No. 4,128,499] and Rodewald's Lewis acid intercalation compounds of graphite [U.S. Pat. Nos. 3,984,352 and 3,962,133].
The conductivity of these intercalated compounds, however, is less than is theoretically possible. The neutral and charged forms of the intercalating agents used as starting materials are in chemical equilibrium and therefore produce intercalation compounds that have both neutral molecules and charged molecules in the interplanar spaces. The neutral molecules do not affect conductivity. Hence, the actual conductivity is derived from the charged form which is present in a lower amount than the amount of agent incorporated.
Therefore, it is an object of the invention to produce an intercalation or lamellar composition of carbon of a graphite-like structure which contains an increased proportion of charged intercalating molecules and through which electrons can move with increased ease. Another object of the invention is to employ a reaction process which allows fast production of the lamellar composition and will permit purification without deintercalation. A further object is to produce lamellar compositions which contain more than one type of charged intercalating molecule.